Lambs, 9 weeks of age, the offspring of sires of the Scottish Blackface, East Friesland, Finnish Landrace, Suffolk and Texel breeds mated to Scottish Blackface females, as a common maternal breed, were given diets containing 12 or 20 mg copper per kg dry matter for 13 weeks. Concentrations of liver copper and of copper and aspartate amino-transferase in the plasma were measured regularly, and the concentrations of copper in the kidney, mandible and cheek muscle were also measured terminally. Livers were examined for histological symptoms of copper toxicity.

Wide breed variation was apparent in liver copper concentration after 6 weeks and in plasma aspartate aminotransferase concentration after 9 weeks. At slaughter, total liver copper and kidney copper concentration showed significant breed variation. For all traits, the Texel-cross lambs had the highest concentrations, followed by the Suffolk crosses, and the Blackface had the lowest. The proportion of ingested copper retained in the liver of the Texel-cross lambs was twice that of the Blackface lambs (0·137 v. 0·056), with the other breed crosses intermediate.

There was a significant difference between diets for liver, kidney and mandible copper concentrations, plasma aspartate amino-transferase concentration, and for total liver copper but not for cheek muscle. Both diets produced elevated plasma aspartate amino-transferase concentration and histological symptoms of copper toxicity in the livers of some lambs.

The results show large breed differences in the susceptibility to copper poisoning, some breeds being at risk when given diets containing 12mg copper per kg dry matter for long periods. There was no suggestion that breeds differed in resistance to poisoning other than through different retentions of copper consumed

Forty-four single- and twin-born New Zealand Corriedale two-tooth ewes and rams aged 14 months were fed individually, in pens, a pelleted ration adjusted to maintain body weight after allowing for wool growth. The sheep were fed for a 3-month settling period, followed by a 3-month experimental period, during which wool growth, fibre diameter, fibre length and net efficiency of wool growth were measured.

Since the wool-growth cycles of the two sexes were found to be out of phase, a valid comparison of the sex data was not possible. Such phase differences may be important in some experimental designs. Significant sex by birth status interactions were identified for all wool production parameters except fibre length, confirming that care must be taken in assigning correction factors during selection of rams and ewes. The general trend was for single-born ewes to produce more and coarser wool more efficiently than twin-born ewes, while the differences between single- and twin-born rams were much smaller. Single-born animals were heavier than twin-born (P<0·01).

Individual values for wool growth and net efficiency varied by a factor of three within sex groups, indicating a considerable scope for selection

An experiment has been carried out at Bahia Blanca to estimate the trend in ovulation rate throughout the year shown by Corriedale ewes of similar live weight in the south-west district of the Argentinian pampa.

Five groups of 16 animals were each subjected to two 20-day observation periods and the 10 observation periods in the experiment were evenly spaced within a year.

The proportion of ewes showing oestrus and ovulation (OO), the frequency of twin ovulations (TO) and, hence, ovulation rate (OR) were estimated for each period by using vasectomized rams and performing laparatomies.

A significant and periodic relationship was found between each trait and the number of days elapsed from the longest day (×). In turn, changes in the values of ×, arising from the progress of the experiment, were to some extent associated with changes in nutrition and surgical interference. However, it was concluded that these factors could not have affected the similar and remarkable seasonality shown by each trait in this study, and that this seasonality was mainly associated with differences in the natural light regime to which the ewes were exposed before and during their corresponding observation periods.

The predicted maximum values for each parameter were reached 1 month before the shortest day. Prior to and after this date both OO and TO declined, so that the predicted OR values became zero for a period of approximately 2 months before the longest day

At the beginning of the autumn breeding season, six Rambouillet ewes were treated with intravaginal pessaries containing 20 mg flurogestone acetate on day 10 (oestrus = day 0) of an oestrous cycle. Sponges were removed after 12 days. Five additional ewes served as untreated controls. Vasectomized rams were used twice daily to detect oestrus and blood samples were collected daily from day 1 until 3 days following the post-treatment oestrus. Animals were slaughtered and reproductive tracts were recovered 3 days after the oestrus followingpessary removal. Epithelial, endometrial and glandular measurements were recorded from sections of oviduct, uterus and cervix using a refrigerated microtome. Serum progesterone was quantified by radioimmunoassay. Intravaginal progestagen treatment prevented ewes from exhibiting oestrus during the period in which pessaries were in place. Oestrus was observed, however, in all treated animals within 2 days of sponge removal, resulting in a mean cycle length (±.e.) of 23·2 (±0·2) days compared with 17·6 (±0·2) days (P<0·01) for controls. Serum progesterone profiles in treated and control animals indicated that corpora lutea regression progressed normally in ewes receiving the exogenous progestagen. Neither reproductive tract weight, ovarian weight, ovulation rate nor follicle number differed between groups (P>0·10). Oviductal, uterine, uterine glandular and cervical epithelial cell heights, as well as uterine glandular proliferation and endometrial thickness, were also similar in treated and control ewes (P>0·10). These data suggest that intravaginal flurogestone acetate does not appreciably alter histology of the reproductive tract during the time in which the fertilized ova would enter the uterus. Overt histological changes, therefore, are not likely to be a significant cause of reduced fertility at a synchronized oestrus.

The proportion of ewes lambing of those exposed to the ram, litter size and weight at lambing, and at weaning, pre-weaning lamb mortality and changes in ewe weight during suckling, were studied in 326 ewes (931 lambings) representing two pure breeds, Oxford and Suffolk, and four crossbreds, Oxford♂ × Suffolk♀, Suffolk♂ × Oxford♀, North Country Cheviot♂ × Oxford♀ and Cheviot♂ × Suffolk♀, mated to purebred and crossbred rams during 9 years. The proportional fertility in the Oxford and Suffolk ewes (0·82 and 0·85 respectively) was lower than that of Suffolk × Oxford (0·93), Oxford × Suffolk (0·94), Cheviot × Oxford (0·88) and Cheviot × Suffolk (0·88) ewes. Litter sizes of Suffolk ewes at birth and at weaning were 1·6 and 1·3 lambs, 0·3 (0·22) and 0·3 (0·27) lambs largeir than those of the Oxford ewes, respectively. The corresponding figures for litter weight were 1·29 kg (0·22) and 11·8 kg (0·36). Oxford ewes lost 0·10 of their weight during nursing compared with 0·14 for the Suffolk and the two reciprocal crosses. The estimates of heterosis in litter size and litter weight at birth were 0·085 and 0·082, and at weaning were 0·13 and 0·18 respectively.

The results showed that Oxford crosses were better in performance than the pure Oxford, whereas the Suffolk crosses were similar in performance to the pure Suffolk, except in the proportion of ewes lambing of those exposed and pre-weaning mortality, in which the crosses were 0·07 and 0·20 superior to the pure Suffolk, respectively.

Breed of sire had a significant effect on litter weight at birth and at weaning, whereas the interaction breed of sire × breed of dam was a significant source of variation on litter size and litter weight at birth and at weaning. Litter performance at birth was significantly lower in 2-year-old ewes and in ewes sired by 3-year-old or older rams than in other age groups

Thirty entire male piglets weaned at 21 days of age were used to study the effects of two levels of dietary protein (178 and 194g/kg), each in combination with five levels of supplemental lysine (0, 1·5, 3·0, 4·5 and 6·0g/kg), in diets given ad libitum and containing 14 MJ digestible energy per kg, on performance from 6 to 20 kg live weight.

Raising total lysine from 7·2 to 8·7 g/kg diet with 178 g crude protein per kg promoted significant increases in average daily gain, efficiency of food conversion and voluntary food intake, and raised all these parameters to levels exhibited by piglets receiving the basal diet containing 194 g crude protein per kg (8·7 g total lysine per kg).

Lysine supplementation of the diet containing 194g crude protein per kg had no effect on growth performance or food intake.

Carcass characteristics at 20 kg live weight were not significantly affected by either dietary crude protein or total lysine (P> 005).

1. An experiment was carried out to describe growth rate, efficiency and thermal balance of pigs accommodated in three different housing conditions during summer in southern Australia.

2. Housed pigs grew at a similar rate to those in an outside pen with a wallow and shelter (418g/day compared with 404g/day respectively; P > 0·05), and both groups utilized food with similar efficiency (food conversion ratios of 3·07 and 3·14 respectively; P > 005). A group accommodated in an outside pen with a wallow but no shelter grew at a significantly slower rate (347g/day; Z <001) with a lower efficiency of food conversion (3·35; P < 005) than either of the other two groups. At slaughter, pigs housed outside without shelter showed a significantly higher dressing proportion (0·749; P < 005) and had less backfat (11·6mm; P < 0·05) than the inside group (0·723 and 13·4mm respectively).

3. Estimated heat storages at 12.00 h of pigs housed inside and outside without shelter were respectively, and approximately, 50 and 18·5 × greater than in those pigs housed outside with shelter.

An auto-immunization procedure selective for boar 5α-androstenone is described. Immunization of boars with a conjugate of androstenone and bovine serum albumin as a carrier protein significantly reduced the accumulation of androstenone in adipose tissue from a mean value of 0·77 (s.e. 0·19)mg/kg fat for untreated boars to 0·24 (s.e. 0·06) mg/kg fat for treated animals. No detrimental side-effects were observed in the immunized animals, and the advantages of male-type growth and carcass characteristics were preserved.

Ultrasonic measurements, using a Danscanner, were taken of the m longissimus dorsi and overlying fat at the 10th and 13th ribs, and 3rd lumbar vertebra, of 50 Hereford bulls with ages ranging from 400 to 600 days, just prior to slaughter and side dissection.

The analysis adjusted the data for live weight and day of slaughter, and the precision of carcass lean and fat prediction was examined. The standard deviations of total fat and lean in the carcass at constant live weight were 40 and 33 g/kg respectively.

The best single measurement of fat depth for predicting fat proportion was fat depth taken 125 mm from the midline at the 13th rib (residual s.d. = 21·8g/kg). The best combined predictors of both total fat and lean proportions in the side were fat depth 125 mm from the midline at the 13th rib, fat depth 75 mm from the midline at the 3rd lumbar vertebra, and fat area at the 10th and 13th ribs, and 3rd lumbar vertebra, with residual s.d. of 20·5 and 19·6 g/kg for fat and lean proportions respectively.

The results confirm that ultrasonic scanning is now able to give a useful indication of the body composition of live cattle.

The age at which the four pairs of permanent incisors emerged, and the interval between first emergence and the attainment of full size, was recorded from observations taken every 2 weeks on 332 female cattle of a herd comprising the Ayrshire, Friesian and Jersey breeds, and the reciprocal crosses among them.

The 1st pair of incisors emerged at a mean age of 101 weeks of age and later pairs at approximately 30-week intervals, with the s.d. increasing proportionately from 7 to 14 weeks. Full size of the incisors was attained, on average, 4·0, 2·4, 3·0 and 5·6 weeks after the initial observations on incisor pairs 1 to 4 respectively.

Breed (or cross) and season of birth significantly affected the age at emergence of the 1st and 2nd pairs of teeth, and breed also affected the age for the 4th pair. Relative to the Friesian breed, an Ayrshire parent delayed emergence of both 1st and 2nd incisor pairs by approximately 4 weeks, and a Jersey parent delayed emergence of all four pairs. The maternal effect was opposite in sign to the effect of breed substitution; in particular, a Jersey dam caused a reduction in the age at emergence. There was no evidence of heterosis in the crosses. On average, each pair of incisors erupted approximately 4 weeks earlier for cows born between October and December than for those born in the period April to June.

Age at calving, lactation length, milk yield, body weights and the ratio of 18-month body weight to that at 42 months (as an estimate of proportion of maturity) were not significantly correlated with the dental traits. Correlations between age at emergence of adjacent incisor pairs were approximately 0·7, a value higher than that between pairs separated by longer time intervals.

An experiment was conducted using two batches of 40 purchased male Hereford × Friesian calves, reared conventionally with weaning after 5 weeks. Five diets were offered ad libitum for 9 weeks: a basic concentrate pellet A offered alone, or with additional chopped or long straw; a diet incorporating 35 g sodium bicarbonate per kg in the basic pellet; and a complete diet with the inclusion of 176g chopped straw (20 mm) per kg in the concentrate pellet.

Concentrate intakes and live-weight gains tended to increase with voluntary intake of roughage and the inclusion of buffer in the diet; giving a complete diet, however, gave the best results, with total intake increased to 1 -6 of that for diet A and also significantly increased weight gains.

Rumen acidity was decreased by roughage consumption or by buffer inclusion in the diet. Increasing roughage consumption tended to promote an increase in the molar proportions of acetic and butyric acids in the rumen liquor, and a decrease in the molar proportion of propionic acid.

Results suggested that chopping the roughage into 20-mm lengths did not obviously alter the rumen-buffering characteristics of long roughage, provided that a greater quantity was included in chopped form.

Two experiments were conducted to compare the effects of single and double suckling on the performance of Hereford × Friesian and Friesian cows at pasture. Double-suckled cows each fostered a Friesian male calf in addition to their own calf. Cows were housed from calving to turnout for 57 and 35 days in experiments 1 and 2 respectively, with corresponding grazing seasons lasting 152 and 146 days. During the grazing season the two suckling treatments were stocked on a series of adjacent plots of equal area, with the occupancy of each plot pair being reversed daily. Live weights, milk yields, herbage intakes, and daylight grazing times and nursing activities were recorded on three occasions 28 days apart.

Double-suckled cows lost significantly more weight than single-suckled cows from calving to turnout in both experiments (39·5 v. 3·3 kg and 45·7 v. 20·6 kg), gained more weight from turnout to weaning in experiment 1 (58·4 v. 23·3 kg) but gained less in experiment 2 (17·5 v. 32·3 kg). Double-suckled cows produced significantly more milk than single-suckled cows: 10·1 v. 8·3 and 13·5 v. 9 1 kg/day in experiments 1 and 2 respectively. Differences in daily milk yield in experiment 2 were apparent 28 days after calving.

Suckling treatments did not influence herbage intakes or daylight grazing times and nursing frequencies. Mean nursing intensities were 1·0 calves per single-suckled cow, compared with 1·8 calves (experiment 1) and 2·2 calves (experiment 2) per double-suckled cow. Double-suckled cows nursed significantly more ‘foreign’ calves than single-suckled cows. Total calf weight at weaning from double-suckled cows in experiments 1 and 2 was respectively 364·6 and 344·4 kg, which was 1·64 of the corresponding weights weaned by single-suckled cows (221·1 and 209·4 kg).

Two experiments were conducted to compare the effects of single and double suckling on the performance of calves at pasture. In association with their own (status 1) calf, each double-suckled cow fostered a Friesian male (status 2) calf during the post-partum housing period. Calf live weights, milk intakes, and daylight grazing times and suckling activities were recorded.

Single-suckled calves were significantly heavier at weaning (221 and 209 kg) than either status 1 (185 and 170 kg) or status 2 (180 and 175 kg) double-suckled calves in experiments 1 and 2 respectively. Daily gains of the single- and status 1 and 2 double-suckled calves were 0·87, 0·69 and 0·61 kg/day in experiment 1, and 0·94, 0·72 and 0·70 kg/day in experiment 2. Single-suckled calves consumed significantly more milk per day during three 28- day periods at pasture than did either status 1 or status 2 double-suckled calves (7·9, 5·2 and 50kg/day, and 90, 7·2 and 6·5 kg/day in experiments 1 and 2). Status effects in the double-suckled calves were not significant for live weights, weight gains or milk intakes.

Double-suckled calves spent more time grazing and sucked their own or assigned foster dams less frequently than did single-suckled calves. Status 2 double-suckled calves spent more time grazing (experiment 1) and sucked for significantly shorter periods from more foreign dams than did their status 1 contemporaries.

It was concluded that double suckling increased annual total weight of calf output per cow but that it was achieved at the expense of individual calf growth performance. Reduced milk intake appeared to be a major factor in limiting live-weight gains in the double-suckled calves.

Rectal temperatures of breeding cows at the National Cattle Breeding Station, ‘Belmont’, Rockhampton were recorded in each of 2 years. The data analysed represented two Bos taurus (Hereford × Shorthorn) and four B. indicus × B. taurus half-bred lines, and 800 to 900 cows in each year. Rectal temperatures averaged 39·8°C, and were 0·5°C higher in British breed than in zebu-cross cows and 0·3°C higher in lactating than in dry British cows (no effect in zebu cross).

Fertility, measured as success or failure in producing a calf at term, was affected by rectal temperature (P<0·0001 in both years). The relationship was curvilinear, the reduction in calving rate due to 01°C increment in temperature being 0009 at 39°C, 002 at 40°C and 0035 at 41°C. Response of fertility to a given change in rectal temperature was the same in different breeds. The average depression of fertility due to heat susceptibility was 015 to 0·25 in British-breed and approximately 010 in zebu-cross herds.

Even in relatively heat-tolerant zebu crossbreds and in a relatively mild environment on the Tropic, both the mean rectal temperature and its genetic variability within a herd had quite large effects on reproduction. The heritability of rectal temperature was 0·25 (s.e. 012) and its genetic correlation with fertility was −0·76 (s.e. 0·35). There was a parallel effect of rectal temperatures of cows on the birth weights of their calves.

The breeding records of 2710 lactating cows, of the Africander (1208), Tswana (542) and Tuli (960) breeds, were analysed to examine the effects of breed and environment on reconception. The reconception rate of Africander cows (0·56) was significantly lower than that of Tswana and Tuli cows (0·80 and 0·81 respectively) (P<0·01). The environmental effects of ranch, calving year, calving period and age/parity all had significant effects on reconception (P<0·01). Interactions between breed and the other main effects were all significant.

The Africander is considered to be a breed of lower fertility than the other two Sanga breeds, the Tswana and Tuli, in Botswana. The results are discussed with respect to determining management interventions to improve cow reproductive performance.

The calving rates, survival and growth of calves of Brahman (344), Bonsmara (454), Simmental (601) and Tuli (276) crossbred cows, and pure Tswana (405), were collected for a 7-year period, 1974–80. Calving and survival rates for calves were 0·90, 0·88, 0·87, 0·87 and 0·82; and 0·94, 0·93, 0·96, 0·94 and 0·93, for Simmental, Tuli, Brahman and Bonsmara crossbreds, and pure Tswana, respectively. These differences were not significant (P<0·05).

Calves produced by Simmental ♂ and Bonsmara ♂ crossbred cows were significantly heavier than those from Brahman ♂ and Tuli ♂ crossbred cows (P<0·01), but not from Tswana-sired calves. At weaning, calves from Simmental-cross cows weighed 214 kg, significantly heavier than those produced by any other cow type (P<0·01). Bonsmara- and Brahman-cross cows produced calves weighing 203 and 198kg respectively at weaning, which were also significantly heavier than the calves of Tswana and Tuli crossbred cows (P<0·01), which weighed 187 and 184 kg respectively.

Productivity estimates combining these three traits, and expressed as weight of calf weaned per cow per year, per kg cow weight and per kg metabolic weight of cow, demonstrate the advantages of three of the crossbred cow types over the pure Tswana. Recommendations for the further development of crossbreeding systems in Botswana are made on the basis of this finding.

Four groups of 12 beef heifers were each given either straw treated with 35 g sodium hydroxide per kg (TS) or untreated straw (US) and were either supplemented with 35 mg monensin per kg (Ms) or not supplemented (Ns). The diet consisted of approximately 0·40 of a concentrate mixture that contained 12·8 MJ metabolizable energy and 243 g crude protein per kg dry matter, and 0·60 straw. Feeding was ad libitum. The average initial weight of the heifers was 207·2 kg and the experiment lasted 86 days.

The average dry matter consumed was 2·3g/kg live weight. Average daily gain (±s.e.) was 505±31·6, 371±33·8, 380±26·2 and 257±32·7g/day for treatment groups TS-Ms, TS-Ns, US-Ms and US-Ns, respectively. These findings indicate that monensin may counteract some ill-effects of diets high in sodium hydroxide-treated straw and thus further research is warranted.

Two farm trials were made to investigate the response to a second implant with the anabolic agent zeranol. Seventy cattle were implanted at the start of the growing period, at 10 to 12 months of age, the remaining 49 cattle being left as controls. Five months later, at the beginning of the fattening period, some cattle from each of the treatments during the growing period were implanted. The response to implantation in both periods was significant on both farms (P<0·05). During the fattening period there was no significant difference in the performance of cattle implanted only at the start of the growing period and that of the control animals, which suggested that the response to the earlier implant was permanent. Although differences in performance during fattening for cattle implanted twice, compared with that for cattle implanted for the first time at the start of fattening, were not statistically significant, on both farms performance was lower for the cattle implanted twice. These results suggest that the response to zeranol in the fattening period may be reduced by approximately 0·30 for cattle previously implanted. Over the combined growing and fattening period, cattle implanted twice showed a significant response in comparison with cattle given only one implant (P < 0·05).

To compare the genetic group differences in live-weight gains, efficiency of food conversion (in terms of dry matter, total digestible nutrients, digestible crude protein, digestible energy and metabolizable energy) and physiological responses related to heat balance, a total of 24 male lambs (91 to 180 days old), four each of Malpura, Sonadi, and their crosses with Dorset and Suffolk breeds, were given a ration having a roughage to concentrate ratio of 250:750g/kg and metabolizable energy content of 100MJ/kg dry matter. Live-weight gain per day was higher and the food conversion ratio (the intakes of total digestible nutrients, digestible energy and metabolizable energy per kg gain) was lower in the crossbreds than in the native sheep. The crossbreds had higher respiratory rates (153 per min) than the natives (140 per min) but there was no significant difference in rectal temperature between purebreds and crossbreds. The crossbred lambs in the present experiment grew faster, consumed more food and utilized the food more efficiently than did the native lambs, despite the fact that they dissipated more energy as body heat. It was, therefore, concluded that the crossbreds performed better than the native breeds between 3 and 6 months of age, even though they were not permanently acclimatized to hot environmental conditions.

Thirty-four pairs of sucking piglets, derived from six sow pairs, within which piglets were cross-fostered shortly after birth, were allotted to either a creep-food treatment or a control (no creep food). Piglets were weaned at 6 weeks of age and all were given a grower diet to slaughter at 9 weeks of age. There were no differences in carcass composition determined on piglets killed at 6 and at 9 weeks. Creep-fed piglets were heavier than controls at 6 and 9 weeks of age, but not at 3 weeks. There were no distinct differences in any of the blood serum samples obtained at 1, 3, 5 and 6 weeks of age for protein and albumin analysis, and zinc sulphate turbidity assay. It was concluded that there was no positive immunological response to the early provision of supplementary nutrients, although there was a positive growth response to creep feeding between 3 weeks of age and weaning at 6 weeks.